This invention relates to semiconductor processing methods, and more particularly it concerns removing undesired material from a semiconductor wafer backside to reduce a risk of inadvertent contamination. The invention also concerns methods of forming integrated circuitry, and in particular methods of forming dynamic random access memory storage capacitors.
Semiconductor processing includes deposition of different materials over a semiconductor wafer. Such materials are typically deposited on a wafer which is placed within a reactor, such as a chemical vapor deposition reactor. During deposition, the material being deposited typically deposits over the entire wafer, including the wafer backside, and on the interior walls of the deposition reactor and the equipment used to support the wafer during processing. Material deposited on the wafer backside is problematic because it can become dislodged during downstream processing and contaminate the frontside of the wafer.
This invention arose out of concerns associated with improving the manner in which semiconductor wafers are processed. This invention also arose out of concerns associated with reducing the chances of inadvertent contamination during semiconductor wafer processing.
Semiconductor processing methods are described which can be used to reduce the chances of an inadvertent contamination during processing. In one implementation, a semiconductor wafer backside is mechanically scrubbed to remove an undesired material prior to forming a final passivation layer over an oppositely facing semiconductor wafer frontside. In another implementation, the wafer backside is treated to remove the undesired material while treatment of the wafer frontside is restricted. In another implementation, the mechanical scrubbing of the wafer backside is conducted in connection with a polishing solution which is effective to facilitate removal of undesired material from the wafer backside. In a preferred implementation, dynamic random access memory storage capacitors are formed and the undesired material constitutes remnant polysilicon which adheres to the wafer backside during formation of a frontside capacitor storage node. In accordance with this implementation, the wafer backside is mechanically scrubbed prior to formation of a storage capacitor dielectric layer, with such mechanical scrubbing taking place in connection with a polishing solution comprising tetramethyl ammonium hydroxide (TMAH) having a desired concentration.